Adaptive Control of Combustion Instabilities in Annular Combustors

Abstract

An adaptive control algorithm based on Lyapunov’s direct method has been implemented in a low-order thermoacoustic network model of an axisymmetric annular combustor. The pressure perturbation at a fixed axial location downstream of the flame — provided by multiple pressure measurements around the combustor circumference — acts as the control input. Control is achieved via modulation of the fuel flow rate at multiple fuel valve locations. New expressions for the controller’s adaptation rates are derived by specifying the desired control settling time: these adaptation rates are functions of known parameters only. Time domain simulations show that the controller successfully stabilises both longitudinal and circumferential modes (including the simultaneous control of multiple unstable modes), even from within the limit cycle. The adaptive controller successfully retains control following a large change in the combustor operating conditions.